Upgrade to Kotlin 2.1.10

- Upgrade kotlinVersion to 2.1.10
- Remove org.jetbrains.kotlin:kotlin-compiler-embeddable from dependencies
- Replace deprecated kotlinOptions with compilerOptions
- Update KotlinConventions of ConventionsPlugin to set Kotlin apiVersion
  and languageVersion to 2.1
- Fix redeclaration error with Kotlin compiler on spring-boot-doc
- Upgrade PluginClasspathGradleBuild to inject missed Kotlin compiler
  related jars

See gh-38539

Signed-off-by: Dmitry Sulman <[email protected]>

Author: dmitrysulman

buildSrc/build.gradle

@@ -42,7 +42,6 @@ dependencies {
 	implementation("org.apache.maven:maven-embedder:${mavenVersion}")
 	implementation("org.antora:gradle-antora-plugin:1.0.0")
 	implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:${kotlinVersion}")
-	implementation("org.jetbrains.kotlin:kotlin-compiler-embeddable:${kotlinVersion}")
 	implementation("org.springframework:spring-context")
 	implementation("org.springframework:spring-core")
 	implementation("org.springframework:spring-web")

buildSrc/src/main/java/org/springframework/boot/build/ConventionsPlugin.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,6 +35,9 @@
  * When the {@link AntoraPlugin} is applied, the conventions in {@link AntoraConventions}
  * are applied.
  *
+ * When the {@code org.jetbrains.kotlin.jvm} plugin is applied, the conventions in
+ * {@link KotlinConventions} are applied.
+ *
  * @author Andy Wilkinson
  * @author Christoph Dreis
  * @author Mike Smithson

buildSrc/src/main/java/org/springframework/boot/build/KotlinConventions.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,7 +25,9 @@
 import org.gradle.api.Project;
 import org.gradle.api.tasks.SourceSet;
 import org.gradle.api.tasks.SourceSetContainer;
-import org.jetbrains.kotlin.gradle.dsl.KotlinJvmOptions;
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget;
+import org.jetbrains.kotlin.gradle.dsl.KotlinJvmCompilerOptions;
+import org.jetbrains.kotlin.gradle.dsl.KotlinVersion;
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompile;
 
 /**
@@ -35,7 +37,7 @@
  * <ul>
  * <li>{@link KotlinCompile} tasks are configured to:
  * <ul>
- * <li>Use {@code apiVersion} and {@code languageVersion} 1.7.
+ * <li>Use {@code apiVersion} and {@code languageVersion} 2.1.
  * <li>Use {@code jvmTarget} 17.
  * <li>Treat all warnings as errors
  * <li>Suppress version warnings
@@ -56,14 +58,14 @@ void apply(Project project) {
 	}
 
 	private void configure(KotlinCompile compile) {
-		KotlinJvmOptions kotlinOptions = compile.getKotlinOptions();
-		kotlinOptions.setApiVersion("1.7");
-		kotlinOptions.setLanguageVersion("1.7");
-		kotlinOptions.setJvmTarget("17");
-		kotlinOptions.setAllWarningsAsErrors(true);
-		List<String> freeCompilerArgs = new ArrayList<>(kotlinOptions.getFreeCompilerArgs());
+		KotlinJvmCompilerOptions kotlinOptions = compile.getCompilerOptions();
+		kotlinOptions.getApiVersion().set(KotlinVersion.KOTLIN_2_1);
+		kotlinOptions.getLanguageVersion().set(KotlinVersion.KOTLIN_2_1);
+		kotlinOptions.getJvmTarget().set(JvmTarget.JVM_17);
+		kotlinOptions.getAllWarningsAsErrors().set(true);
+		List<String> freeCompilerArgs = new ArrayList<>(kotlinOptions.getFreeCompilerArgs().get());
 		freeCompilerArgs.add("-Xsuppress-version-warnings");
-		kotlinOptions.setFreeCompilerArgs(freeCompilerArgs);
+		kotlinOptions.getFreeCompilerArgs().set(freeCompilerArgs);
 	}
 
 	private void configureDokkatoo(Project project) {

gradle.properties

@@ -14,7 +14,7 @@ hamcrestVersion=3.0
 jacksonVersion=2.18.2
 javaFormatVersion=0.0.43
 junitJupiterVersion=5.11.4
-kotlinVersion=1.9.25
+kotlinVersion=2.1.10
 mavenVersion=3.9.4
 mockitoVersion=5.15.2
 nativeBuildToolsVersion=0.10.5

spring-boot-project/spring-boot-dependencies/build.gradle

@@ -1193,8 +1193,9 @@ bom {
 	}
 	library("Kotlin", "${kotlinVersion}") {
 		prohibit {
-			versionRange "[2.0.0-Beta1,)"
-			because "it exceeds our baseline"
+			contains "-Beta"
+			contains "-RC"
+			because "we don't want betas or release candidates"
 		}
 		group("org.jetbrains.kotlin") {
 			imports = [

spring-boot-project/spring-boot-docs/build.gradle

@@ -1,3 +1,5 @@
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
 plugins {
 	id "dev.adamko.dokkatoo-html"
 	id "java"
@@ -304,6 +306,26 @@ task runLoggingFormatExample(type: org.springframework.boot.build.docs.Applicati
 	normalizeTomcatPort()
 }
 
+// To avoid a redeclaration error with Kotlin compiler
+tasks.withType(KotlinCompile) {
+	javaSources.from = [
+			"src/main/java/org/springframework/boot/docs/data/nosql/cassandra/connecting/User.java",
+			"src/main/java/org/springframework/boot/docs/features/devservices/testcontainers/atdevelopmenttime/importingcontainerdeclarations/MyContainers.java",
+			"src/main/java/org/springframework/boot/docs/features/externalconfig/typesafeconfigurationproperties/usingannotatedtypes/Server.java",
+			"src/main/java/org/springframework/boot/docs/features/springapplication/applicationavailability/managing/CacheCompletelyBrokenException.java",
+			"src/main/java/org/springframework/boot/docs/packaging/nativeimage/advanced/nestedconfigurationproperties/Nested.java",
+			"src/main/java/org/springframework/boot/docs/using/springbeansanddependencyinjection/multipleconstructors/AccountService.java",
+			"src/main/java/org/springframework/boot/docs/using/springbeansanddependencyinjection/multipleconstructors/RiskAssessor.java",
+			"src/main/java/org/springframework/boot/docs/using/springbeansanddependencyinjection/singleconstructor/AccountService.java",
+			"src/main/java/org/springframework/boot/docs/using/springbeansanddependencyinjection/singleconstructor/RiskAssessor.java",
+			"src/main/java/org/springframework/boot/docs/using/usingthespringbootapplicationannotation/individualannotations/AnotherConfiguration.java",
+			"src/main/java/org/springframework/boot/docs/using/usingthespringbootapplicationannotation/individualannotations/SomeConfiguration.java",
+			"src/main/java/org/springframework/boot/docs/web/servlet/springmvc/errorhandling/MyErrorBody.java",
+			"src/main/java/org/springframework/boot/docs/web/servlet/springmvc/errorhandling/MyException.java",
+			"src/main/java/org/springframework/boot/docs/web/servlet/springmvc/errorhandling/SomeController.java",
+	]
+}
+
 def getRelativeExamplesPath(var outputs) {
 	def fileName = outputs.files.singleFile.name
 	'example$example-output/' + fileName

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/build.gradle

@@ -54,7 +54,6 @@ dependencies {
 	testImplementation("org.assertj:assertj-core")
 	testImplementation("org.graalvm.buildtools:native-gradle-plugin")
 	testImplementation("org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion")
-	testImplementation("org.jetbrains.kotlin:kotlin-compiler-embeddable:$kotlinVersion")
 	testImplementation("org.jetbrains.kotlin:kotlin-compiler-runner:$kotlinVersion")
 	testImplementation("org.jetbrains.kotlin:kotlin-daemon-client:$kotlinVersion")
 	testImplementation("org.junit.jupiter:junit-jupiter")

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/KotlinPluginAction.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -49,7 +49,7 @@ private String getKotlinVersion(Project project) {
 	private void enableJavaParametersOption(Project project) {
 		project.getTasks()
 			.withType(KotlinCompile.class)
-			.configureEach((compile) -> compile.getKotlinOptions().setJavaParameters(true));
+			.configureEach((compile) -> compile.getCompilerOptions().getJavaParameters().set(true));
 	}
 
 	@Override

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/plugin/KotlinPluginActionIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -83,7 +83,7 @@ void taskConfigurationIsAvoided() throws IOException {
 				configured.add(line.substring("Configuring :".length()));
 			}
 		}
-		assertThat(configured).containsExactlyInAnyOrder("help", "compileJava", "clean");
+		assertThat(configured).containsExactlyInAnyOrder("help", "clean");
 	}
 
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/testkit/PluginClasspathGradleBuild.java

@@ -18,6 +18,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
@@ -33,9 +34,12 @@
 import org.apache.hc.core5.http.HttpRequest;
 import org.apache.hc.core5.http2.HttpVersionPolicy;
 import org.gradle.testkit.runner.GradleRunner;
+import org.gradle.util.GradleVersion;
+import org.jetbrains.kotlin.buildtools.api.jvm.ClassSnapshotGranularity;
 import org.jetbrains.kotlin.gradle.model.KotlinProject;
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilerPluginSupportPlugin;
 import org.jetbrains.kotlin.gradle.plugin.KotlinPlatformJvmPlugin;
+import org.jetbrains.kotlin.konan.target.HostManager;
 import org.jetbrains.kotlin.project.model.LanguageSettings;
 import org.jetbrains.kotlin.tooling.core.KotlinToolingVersion;
 import org.tomlj.Toml;
@@ -55,6 +59,8 @@
  */
 public class PluginClasspathGradleBuild extends GradleBuild {
 
+	private static final GradleVersion GRADLE_VERSION_8_10 = GradleVersion.version("8.10");
+
 	public PluginClasspathGradleBuild() {
 		super();
 	}
@@ -69,6 +75,15 @@ public GradleRunner prepareRunner(String... arguments) throws IOException {
 	}
 
 	private List<File> pluginClasspath() {
+		List<File> pluginClasspath = new ArrayList<>(basePluginClasspath());
+		if (this.getGradleVersion() == null
+				|| GradleVersion.version(this.getGradleVersion()).compareTo(GRADLE_VERSION_8_10) > 0) {
+			pluginClasspath.addAll(classpathAdditionsForGradleVersionsWithEmbeddedKotlin2());
+		}
+		return pluginClasspath;
+	}
+
+	private List<File> basePluginClasspath() {
 		return Arrays.asList(new File("bin/main"), new File("build/classes/java/main"),
 				new File("build/resources/main"), new File(pathOfJarContaining(LaunchScript.class)),
 				new File(pathOfJarContaining(ClassVisitor.class)),
@@ -94,6 +109,12 @@ private List<File> pluginClasspath() {
 				new File(pathOfJarContaining("org.graalvm.buildtools.utils.SharedConstants")));
 	}
 
+	private List<File> classpathAdditionsForGradleVersionsWithEmbeddedKotlin2() {
+		return Arrays.asList(new File(pathOfJarContaining(ClassSnapshotGranularity.class)),
+				new File(pathOfJarContaining("org.jetbrains.kotlin.build.report.metrics.GradleBuildTime")),
+				new File(pathOfJarContaining(HostManager.class)));
+	}
+
 	private String pathOfJarContaining(String className) {
 		try {
 			return pathOfJarContaining(Class.forName(className));

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/plugin/KotlinPluginActionIntegrationTests-kotlinCompileTasksCanOverrideDefaultJavaParametersFlag.gradle

@@ -4,16 +4,16 @@ plugins {
 
 apply plugin: 'org.jetbrains.kotlin.jvm'
 
-import org.jetbrains.kotlin.gradle.dsl.KotlinCompile
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 tasks.withType(KotlinCompile) {
-	kotlinOptions.javaParameters = false
+	compilerOptions.javaParameters = false
 }
 
 task('kotlinCompileTasksJavaParameters') {
 	doFirst {
 		tasks.withType(KotlinCompile) {
-			println "${name} java parameters: ${kotlinOptions.javaParameters}"
+			println "${name} java parameters: ${compilerOptions.javaParameters.get()}"
 		}
 	}
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/plugin/KotlinPluginActionIntegrationTests-kotlinCompileTasksUseJavaParametersFlagByDefault.gradle

@@ -4,12 +4,12 @@ plugins {
 
 apply plugin: 'org.jetbrains.kotlin.jvm'
 
-import org.jetbrains.kotlin.gradle.dsl.KotlinCompile
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 task('kotlinCompileTasksJavaParameters') {
 	doFirst {
 		tasks.withType(KotlinCompile) {
-			println "${name} java parameters: ${kotlinOptions.javaParameters}"
+			println "${name} java parameters: ${compilerOptions.javaParameters.get()}"
 		}
 	}
 }